It has been documented that significant amounts of tropical precipitation are concentrated in coastal areas, which is especially prominent over the western coast of Sumatra Island. We conducted 14-day-long numerical simulations, focusing on precipitation patterns around Sumatra Island. In the control experiment, the rainfall concentration was obscure, and dry biases were found. Based on the budget equation of the column-integrated frozen moist static energy (which is nearly equivalent to the column-integrated moisture under the weak temperature gradient assumption), we formulated 9 sensitivity experiments. When the terminal velocity and effective radius of ice clouds were reduced in addition to incorporating the warmer sea surface temperature (SST) around the coast, the model showed better rainfall peak fidelity. On the other hand, similar diurnal cycles of precipitation were simulated in the sensitivity tests without any conspicuous peaks in the coastal region, which indicated that the precipitation concentration fidelity was irrelevant to that of the diurnal cycle. An analysis in the time-mean fields demonstrated that inhibition of radiative cooling (associated with the upper-level ice clouds) and warmer SSTs induced anomalous updrafts, and thus, more moisture and precipitation were brought to the coast by enhancement of the vertical moisture advection. Comparing the simulation results with in situ observations, we speculated that together with the climatologically warmer SSTs, the SST diurnal cycle and lateral transport of ice clouds from inland convection, which was strictly regulated by solar insolation, significantly contributed to the precipitation concentration around the coastal region.